276 ANNUAL EEPORT SMITPISONIAN INSTITUTION, 1908. 



by Sigurd Nauckhoff,** showing why nitroglycerin can sometimes be 

 subjected to intense cooling without freezing (supercooling), and to 

 a paper by Dr. H. Kast,^ showing that there are two kinds of nitro- 

 glycerin (one being an allotropic modification), with two dift'erent 

 melting jooints, one nitroglycerin solidifying at about 13.2° and the 

 other at about 2.1°, the melting points being 13.5° and 2.5°, re- 

 spectively. 



Professor Will found that dinitroglycerin is not a sure guaranty 

 against solidification, and that under certain conditions explosives 

 prepared with it may become solid at a higher temperature than 

 trinitroglycerin exj^losives. 



Of all these additions none has so far been definitely adopted for 

 the manufacture of unfreezable dynamites, but, I believe that lately 

 dinitrodichlorhydrine has been used with considerable success b}^ the 

 German works of the Nobel companies. 



We now come to gun cotton. The really important step in the 

 manufacture of gun cotton was taken when the British Government 

 adopted a process of pulping and purifying the gun cotton, first 

 patented by John Tonkin, jr., of Poole, near Copperhouse, in Corn- 

 wall,'' and again in combination with the compression of the pulped 

 gun cotton, three years later, by Sir Frederick Abel.'^ The next step 

 was made when the principle of the detonation of nitrocompounds 

 by means of a small fulminate of mercury charge, invented by Alfred 

 Nobel,*^ was extended by Mr. Brown, Sir Frederick Abel's assistant, 

 to gim cotton.'' 



Baron von Lenck, the Austrian general, who worked most assidu- 

 ously as the pioneer of Schonbein's invention, used gun cotton in 

 hanks; the British Government introduced the use of cotton waste 

 from spinning and other operations where threads are made. The 

 reason for this change is not quite apparent, unless it was felt that 

 since the cotton had to be j^ulped in any case the cheaper waste might 

 do just as well as the long threads. This use of cotton waste has con- 

 tinued ever since. 



It is very curious that in the jDurchase and use of nitric and sul- 

 phuric acid for the nitration of gun cotton most stringent conditions 

 are laid down with regard to freedom from mineral matter, chlorine, 

 sulphates, arsenic, etc. Yet, as far as I could ascertain, no special 

 precautions seem to be taken in the case of cotton to guard against 



«" Zeitschrift fiir angewandte Chemie," 1005, p. 11. 



^ " Zeitschrift f. d. ges. Scliiess u. Sprenggtoffweseu," 190G, p. 225. 



c British patent, No. 320, of 1862. 



^ Id., No. 1102, of 1865. 



« Id.,- No. 1345, of 1867. 



f Id., No. 3115, of 1868. 



